Imaging device and imaging module

ABSTRACT

An imaging device includes a pixel cell including a photoelectric conversion layer having first and second surfaces, a pixel electrode on the first surface, an auxiliary electrode on the first surface, the auxiliary electrode surrounding the pixel electrode and being electrically insulated from the pixel electrode, a counter electrode on the second surface, and a charge detection circuit connected to the pixel electrode; a voltage supply circuit; a first switch switching between electrical connection and disconnection; a first capacitor having one end connected to the auxiliary electrode and the other end held to a predetermined voltage; and a first control circuit connected to the first switch, the first control circuit causing the first switch to switch between electrical connection and disconnection. The voltage supply circuit is connected, through the first switch, to the auxiliary electrode of the first pixel cell and to the one end of the first capacitor.

BACKGROUND 1. Technical Field

The present disclosure relates to an imaging device and an imagingmodule.

2. Description of the Related Art

A technology proposed in recent years is to expand a dynamic range incharge-coupled device (CCD) image sensors, complementarymetal-oxide-semiconductor (CMOS) image sensors, and other imagingdevices. Japanese Patent No. 4018820, for example, discloses an imagingdevice in which a dynamic range can be expanded by placinghigh-sensitivity pixel cells and low-sensitivity pixel cells in animaging area. In the imaging device disclosed in Japanese Patent No.4018820, a photodiode having a large area is placed in ahigh-sensitivity pixel cell and a photodiode having a small area isplaced in a low-sensitivity pixel cell.

SUMMARY

One non-limiting and exemplary embodiment in this application providesan imaging device that suppresses saturation in pixel cells under highilluminance to enable wide dynamic range photography.

In one general aspect, the techniques disclosed here feature an imagingdevice that includes at least one pixel cell that includes a first pixelcell, each of the at least one pixel cell including a photoelectricconversion layer having a first surface and a second surface opposite tothe first surface, a pixel electrode on the first surface, an auxiliaryelectrode on the first surface, the auxiliary electrode surrounding thepixel electrode and being electrically insulated from the pixelelectrode, a counter electrode on the second surface, the counterelectrode facing both of the pixel electrode and the auxiliaryelectrode, and a charge detection circuit connected to the pixelelectrode; a voltage supply circuit that supplies a voltage; a firstswitch that switches between electrical connection and electricaldisconnection; a first capacitor that has one end connected to theauxiliary electrode of the first pixel cell and the other end held to apredetermined voltage; and a first control circuit connected to thefirst switch, the first control circuit causing the first switch toswitch between electrical connection and electrical disconnection. Thevoltage supply circuit is connected, through the first switch, to theauxiliary electrode of the first pixel cell and to the one end of thefirst capacitor.

It should be noted that general or specific embodiments may beimplemented as an element, a device, a module, a system, an integratedcircuit, a method, or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually provided by the various embodiments orfeatures disclosed in the specification and drawings, which need not allbe provided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates the structure of an imaging deviceaccording to a first embodiment;

FIG. 2A schematically illustrates an example of the layout of a pixelelectrode and an auxiliary electrode in the pixel cell in FIG. 1;

FIG. 2B is a schematic cross-sectional view illustrating the devicestructures of the pixel cells in FIG. 1;

FIG. 3 illustrates a plurality of capacitors and a voltage supplycircuit that are included in the imaging device according to the firstembodiment;

FIG. 4 schematically illustrates a relationship between sensitivityoutput and voltage applied to the auxiliary electrode in the pixel cell;

FIG. 5A schematically illustrates electrical connections between avoltage supply circuit and auxiliary electrodes in pixel cells in animaging device according to a second embodiment;

FIG. 5B is a timing diagram illustrating timing when the voltage supplycircuit changes voltages in the imaging device in the second embodiment;

FIG. 6A schematically illustrates electrical connections among auxiliaryelectrodes, a voltage supply circuit, a row scanning circuit, and acolumn scanning circuit in an imaging device according to a thirdembodiment;

FIG. 6B is a timing diagram illustrating timing when the voltage supplycircuit changes voltage for each area in the imaging device according tothe third embodiment;

FIG. 7A schematically illustrates electrical connections among auxiliaryelectrodes, a row scanning circuit, and a voltage supply circuit in animaging device in a fourth embodiment;

FIG. 7B is a timing diagram illustrating timing when the voltage supplycircuit changes voltage for each area in the imaging device according tothe fourth embodiment; and

FIG. 8 is a schematic block diagram illustrating the structure of animaging module according to a fifth embodiment.

DETAILED DESCRIPTION

In the imaging device described in Japanese Patent No. 4018820, it isdifficult to dynamically lower the sensitivity of the pixel cell.Therefore, if illuminance is very high, charges generated in the pixelcell are saturated, lowering the dynamic range. One non-limiting andexemplary embodiment in this application provides an imaging device thatenables wide dynamic range photography.

The present disclosure includes an imaging device and an imaging moduledescribed in items below.

Item 1

An imaging device that includes:

at least one pixel cell that includes a first pixel cell, each of the atleast one pixel cell including

-   -   a photoelectric conversion layer having a first surface and a        second surface opposite to the first surface,    -   a pixel electrode on the first surface,    -   an auxiliary electrode on the first surface, the auxiliary        electrode surrounding the pixel electrode and being electrically        insulated from the pixel electrode,    -   a counter electrode on the second surface, the counter electrode        facing both of the pixel electrode and the auxiliary electrode,        and    -   a charge detection circuit connected to the pixel electrode;

a voltage supply circuit that supplies a voltage;

a first switch that switches between electrical connection andelectrical disconnection;

a first capacitor that has one end connected to the auxiliary electrodeof the first pixel cell and the other end held to a predeterminedvoltage; and

a first control circuit connected to the first switch, the first controlcircuit causing the first switch to switch between electrical connectionand electrical disconnection, wherein

the voltage supply circuit is connected, through the first switch, tothe auxiliary electrode of the first pixel cell and to the one end ofthe first capacitor.

Item 2

In the imaging device according to item 1,

the at least one pixel cell includes a second pixel cell, and

the auxiliary electrode of the second pixel cell is connected to theauxiliary electrode of the first pixel cell and to the one end of thefirst capacitor, and

the voltage supply circuit is connected, through the first switch, tothe auxiliary electrode of the second pixel cell.

Item 3

The imaging device according to item 1 further including:

a second capacitor;

a second switch that switches between electrical connection andelectrical disconnection; and

a second control circuit connected to the second switch, the secondcontrol circuit causing the second switch to switch between electricalconnection and electrical disconnection, wherein

the at least one pixel cell includes a second pixel cell,

the second capacitor has one end connected to the auxiliary electrode ofthe second pixel cell and the other end held to a predetermined voltage,

the voltage supply circuit applies a first voltage to the auxiliaryelectrode of the first pixel cell through the first switch, and

the voltage supply circuit applies a second voltage different from thefirst voltage, to the auxiliary electrode of the second pixel cellthrough the second switch.

Item 4

In the imaging device according to item 1 or 2, the voltage supplycircuit includes the first switch.

Item 5

In the imaging device according to item 3, the voltage supply circuitincludes the first switch and the second switch.

Item 6

In the imaging device according to any one of items 1 to 5,

the first control circuit includes a first scanning circuit and a secondscanning circuit, the first scanning circuit and the second scanningcircuit being connected to the first switch, and

the first switch switches between electrical connection and electricaldisconnection based on both of a signal from the first scanning circuitand a signal from the second scanning circuit.

Item 7

In the imaging device according to any one of items 1 to 5,

the first control circuit includes a first scanning circuit connected tothe first switch, and

the first switch switches between electrical connection and electricaldisconnection based on a signal from the first scanning circuit.

Item 8

An imaging module that includes

the imaging device according to any one of items 1 to 7, and

a camera signal processor that generates image data by processing animage signal output from the imaging device.

The present disclosure further includes an imaging device and an imagingmodule described in items below.

Item 1

An imaging device including a plurality of pixel cells and capacitances,each of which is provided in correspondence to one of at least two ofthe plurality of pixel cells; each of the plurality of pixel cells has apixel electrode, an auxiliary electrode disposed around the pixelelectrode in a plan view of the pixel electrode so as to be electricallyinsulated from the pixel electrode, a counter electrode opposite to thepixel electrode and auxiliary electrode, and a photoelectric conversionfilm sandwiched between the counter electrode and the pixel electrodeand between the counter electrode and the auxiliary electrode,photoelectric conversion film converting light to charges; eachcapacitance is connected to the auxiliary electrode in the correspondingpixel cell.

Thus, since a capacitance is connected to the auxiliary electrode ineach of at least two pixel cells, a voltage can be individually appliedto each capacitance and can be held in it. This enables the sensitivityof each of a plurality of pixel cells to be dynamically adjustedindividually. Therefore, the sensitivity of a pixel cell havingextremely high illuminance, for example, can be dynamically kept low.Accordingly, saturation of charges generated in the pixel cell can besuppressed, and this enables wide dynamic range photography.

Since the voltage applied to each capacitance is held, the sensitivityof each pixel cell to which a capacitance is connected can bemaintained. Therefore, global shuttering becomes possible, in whichexposures start at the same time, for a plurality of pixels havingdifferent sensitivities.

Item 2

In the imaging device according to item 1, the plurality of pixel cellsare placed in an imaging area that includes a first area in which aplurality of first pixel cells are placed and a second area in which aplurality of second pixels are placed; the plurality of capacitancesincludes a first capacitance connected to the auxiliary electrodes intwo first pixel cells and a second capacitance connected to theauxiliary electrodes in two second pixel cells.

Thus, since a capacitance common to a plurality of pixel cells in eachof two areas in the imaging area is provided, sensitivities can beindividually adjusted for the plurality of pixel cells in each of thetwo areas. In photography in which different sensitivities are set forpixel cells in an even-numbered column and pixel cells in anodd-numbered column, for example, two types of images having differentsensitivities, that is, an image corresponding to the pixel cells in theeven-numbered column and an image corresponding to the pixel cells inthe odd-numbered column, are obtained in one photography.

Item 3

The imaging device according to item 1, further including a voltagesupply circuit that applies voltages to a plurality of capacitances.

Thus, since the imaging device has a voltage supply circuit, anindividual voltage can be applied to each capacitance without having toexternally provide a voltage supply circuit.

Item 4

The imaging device according to item 1, further including switches, eachof which is provided for each capacitance and is connected to thecorresponding capacitance, wherein the voltage supply circuitindividually applies a voltage to each capacitance through thecorresponding switch.

Thus, individual voltages can be applied to the capacitances by a singlevoltage supply circuit, and this enables a voltage supply circuit to besimplified.

Item 5

In the imaging device according to item 4, the plurality of pixel cellsare placed in a matrix, a capacitance is provided for each pixel cell,and the imaging device further has a scanning circuit that drivesswitches on a per-row or per-column basis.

Thus, since voltages can be applied to capacitances on a per-row orper-column basis, application of voltages to all of the pixel cells iscompleted at high speed.

Item 6

In the imaging device according to item 5, the voltage supply circuithas voltage appliers, each of which is provided for one column andapplies a voltage to the capacitances provided for the pixel cellsplaced in the column through switches provided for the pixel cells; thescanning circuit drives switches on a per-row basis.

Thus, since an individual voltage can be applied to the capacitanceprovided for each pixel cell in the active matrix method. Therefore,application of voltages to all of the pixel cells is completed at highspeed and with various sensitivity settings.

Item 7

An imaging module that includes the imaging device according to any oneof items 1 to 6 and a camera signal processor that processes an imagesignal output from the imaging device and creates image data.

Thus, an imaging module having an imaging device that enables widedynamic range photography is implemented.

Embodiments will be specifically described with reference to thedrawings. All embodiments described below illustrate general or specificexamples. Numerals, shapes, materials, constituent elements, theplacement positions and connection forms of these constituent elements,processing timings, and the like are only examples, and are not intendedto restrict the present disclosure. Of the constituent elementsdescribed in the embodiments below, constituent elements not describedin independent claims, each of which indicates the topmost concept, willbe described as optional constituent elements.

First Embodiment

The structure and functions of an imaging device according to a firstembodiment will be described with reference to FIGS. 1 to 4.

Structure of the Imaging Device

FIG. 1 schematically illustrates the structure of the imaging device 1according to the first embodiment. Typically, the imaging device 1 hasan imaging area 200 in which a plurality of pixel cells are placed in amatrix, a row scanning circuit 201, a controller 202, a signalprocessing circuit 203, and an output circuit 204. The imaging area 200has first areas in which a plurality of pixel cells 100 are placed andsecond areas in which a plurality of pixel cells 101 are placed. In thedescription below, the plurality of pixel cells 100 in the first areasand the plurality of pixel cells 101 in the second areas will sometimesbe referred to as the plurality of pixel cells. Here, the plurality ofpixel cells 100 in the first areas and the plurality of pixel cells 101in the second area constitute all pixel cells in the imaging area 200.The imaging device 1 is typically an image sensor implemented by asingle semiconductor chip.

In this embodiment, the imaging device 1 further includes capacitances,each of which is provided in correspondence to one of at least two ofthe plurality of pixel cells, and a voltage supply circuit that appliesa voltage to each capacitance. The capacitance indicates a capacitor.However, a parasitic capacitance may be used. These capacitances andvoltage supply circuit will be described later with reference to FIG. 3.

As illustrated in FIG. 1, the plurality of pixel cells 100 are placed ineven-numbered columns and the plurality of pixel cells 101 are placed inodd-numbered columns, for example. That is, in FIG. 1, a first area isan even-numbered column and a second area is an odd-numbered column. Theplurality of cells may be placed in one dimension. In this case, theimaging device 1 may be a line sensor.

The row scanning circuit 201 is connected to the plurality of pixelcells 100 and the plurality of pixel cells 101 through various controllines. The row scanning circuit 201 selects a plurality of pixel cellsplaced in one row at a time, reads out a signal voltage, and resets thepotentials of the pixel electrodes. The row scanning circuit 201 is alsoreferred to as the vertical scanning circuit. The controller 202controls the whole of the imaging device 1.

The signal processing circuit 203 performs signal processing on thesignal voltage read out from each pixel cell. Specifically, the signalprocessing circuit 203 performs noise reduction signal processingtypified by correlated double sampling, analog-digital (AD) conversion,and other processing.

The output circuit 204 outputs a signal voltage resulting from theprocessing by the signal processing circuit 203 to the outside of theimaging device 1.

Device Structure of Each Pixel Cell

FIG. 2A schematically illustrates an example of the layout of a pixelelectrode 102 and an auxiliary electrode 103 included in the pixel cell100 and an example of the layout of a pixel electrode 112 and anauxiliary electrode 113 included in the pixel cell 101. FIG. 2B is aschematic cross-sectional view illustrating the device structures of thepixel cell 100 and pixel cell 101. In the layout examples in FIG. 2A andthe device structures in FIG. 2B, there is no difference between thepixel cell 100 and pixel cell 101. Therefore, in descriptions givenbelow with reference to FIGS. 2A and 2B, the pixel electrode 102 will bedescribed as a representative of the pixel electrode 102 and pixelelectrode 112, and the auxiliary electrode 103 will be described as arepresentative of the auxiliary electrode 103 and auxiliary electrode113.

The pixel cell 100 and pixel cell 101 each include a semiconductorsubstrate 212, a readout circuit 211, and a photoelectric convertor 115.The semiconductor substrate 212 is, for example, a p-type siliconsubstrate. The readout circuit 211 detects a signal charge captured bythe pixel electrode 102 and outputs a signal voltage matching the signalcharge. The readout circuit 211 typically includes an amplifyingtransistor, a reset transistor, an address transistor, and the like. Thereadout circuit 211 is formed on the semiconductor substrate 212.

An inter-layer insulating layer 210 is laminated on the front surface ofthe semiconductor substrate 212. In the inter-layer insulating layer210, a contact plug 116, which electrically interconnects the readoutcircuit 211 and pixel electrode 102, various wires, and the like areburied.

The photoelectric convertor 115 is disposed on the inter-layerinsulating layer 210. The photoelectric convertor 115 includes the pixelelectrode 102, the auxiliary electrode 103, a counter electrode 105disposed opposite to pixel electrode 102 and auxiliary electrode 103,and a photoelectric conversion film 104. The photoelectric conversionfilm 104 is sandwiched between the counter electrode 105 and the pixelelectrode 102 and between the counter electrode 105 and the auxiliaryelectrode 103. In other words, the pixel electrode 102 and auxiliaryelectrode 103 are placed on a first surface of the photoelectricconversion film 104, and the counter electrode 105 is placed on a secondsurface of the photoelectric conversion film 104, the second surfacebeing opposite to the first surface.

The counter electrode 105 is formed from, for example, a conductivetransparent material such as an indium tin oxide (ITO) material. Thepixel electrode 102 and auxiliary electrode 103 are formed frompolysilicon that has conductivity given by doping a metal or animpurity. Examples of metals include aluminum and copper. Although notillustrated, the pixel cells 100 and 101 may have, on the counterelectrode 105, a color filter and a microlens that collects light.

As illustrated in FIG. 2A, the pixel electrode 102 has a rectangularshape and the auxiliary electrode 103 has a rectangular ring shape thatencloses the pixel electrode 102. Like this, in this embodiment, theauxiliary electrode 103 is continuously formed so as to enclose thepixel electrode 102. The pixel electrode 102 and auxiliary electrode 103are separated by a predetermined distance with a spacing interveningtherebetween. That is, the auxiliary electrode 103 is disposed aroundthe pixel electrode 102 in a plan view so as to be electricallyinsulated from the pixel electrode 102.

Now, the principle of the modulation of the sensitivity of the pixelcell 100 and pixel cell 101 will be described in detail. In thisembodiment, the imaging device 1 detects the positive hole of anelectron-hole pair generated by photoelectric conversion in thephotoelectric conversion film 104 as a signal charge. However, theimaging device 1 may detect the electron as the signal charge.

The photoelectric conversion film 104 converts light into charges. Thesensitivities of the pixel cells 100 and 101 are modulated by anelectric field generated by a difference in potential between the pixelelectrode 102 and the counter electrode 105 and an electric fieldgenerated by a difference in potential between the auxiliary electrode103 and the counter electrode 105. A case will be considered in whichthe potentials of the pixel electrode 102 and auxiliary electrode 103are set so as to be lower than the potential of the counter electrode105 and in which a difference in potential between the pixel electrode102 and the counter electrode 105 and a difference in potential betweenthe auxiliary electrode 103 and the counter electrode 105 are generated.In this case, positive holes generated in the photoelectric conversionfilm 104 by photoelectric conversion move to the pixel electrode 102 andauxiliary electrode 103. If, for example, the difference in potentialbetween the pixel electrode 102 and the counter electrode 105 is largerthan the difference in potential between the auxiliary electrode 103 andthe counter electrode 105, charges (positive holes, in this example)generated in the photoelectric conversion film 104 in the vicinity ofthe auxiliary electrode 103 are likely to flow into the pixel electrode102 and are less likely to flow into the auxiliary electrode 103. As aresult, these charges are read out by the readout circuit 211 connectedto the pixel electrode 102 and contribute to the sensitivity of thepixel cell 100 in the first area.

By contrast, if the difference in potential between the pixel electrode102 and the counter electrode 105 is smaller than the difference inpotential between the auxiliary electrode 103 and the counter electrode105, charges generated in the photoelectric conversion film 104 in thevicinity of the auxiliary electrode 103 are likely to flow into theauxiliary electrode 103 and are less likely to flow into the pixelelectrode 102. Of the charges generated in the vicinity of the auxiliaryelectrode 103, charges that have flowed into the auxiliary electrode 103do not contribute to the sensitivity of the pixel cell 100. In otherwords, if the difference in potential between the pixel electrode 102and the counter electrode 105 is smaller than the difference inpotential between the auxiliary electrode 103 and the counter electrode105, the size of the effective sensitivity area of the pixel cell 100becomes narrower than in a case in which the difference in potentialbetween the pixel electrode 102 and the counter electrode 105 is largerthan the difference in potential between the auxiliary electrode 103 andthe counter electrode 105. The effective sensitivity area is asubstantial light receiving area of the photoelectric conversion film,the substantial light receiving area being one of the factors thatdetermine the sensitivity of a pixel cell.

The photoelectric conversion film 104 is typically formed from anorganic material. An example of an organic material has a structure inwhich a p-type organic semiconductor and an n-type organic semiconductorare joined together. As the p-type organic semiconductor, anelectron-releasing organic compound can be used. Examples ofelectron-releasing organic compounds include triarylamine compounds,benzidine compounds, and pyrazoline compounds. As the n-type organicsemiconductor, an electron-accepting compound can be used. Examples ofelectron-accepting compounds include condensed aromatic carbocycliccompounds, polyarylene compounds, and five- to seven-memberedheterocycle compounds including a nitrogen atom, an oxygen atom, or asulfur atom.

FIG. 3 illustrates capacitances 140 and 141 and a voltage supply circuit130 that are included in the imaging device 1 according to thisembodiment. This drawing schematically illustrates electricalconnections among the voltage supply circuit 130, the auxiliaryelectrodes 103 in two pixel cells 100 and 100 a in the first area, andthe auxiliary electrodes 113 in two pixel cells 101 and 101 a in thesecond area.

The voltage supply circuit 130 has two voltage appliers 130 a and 130 b,each of which independently generates a predetermined voltage. Thus, anindividual voltage can be applied to each of a plurality of pixel cellsincluding the two pixel cells 100 and 100 a and to each of a pluralityof pixel cells including the two pixel cells 101 and 101 a. Theintensities of voltages applied to the pixel cells 100 and 100 a and thepixel cells 101 and 101 a are appropriately determined in response to,for example, commands entered by the manipulator manipulating theimaging device 1 or commands from the controller 202 (see FIG. 1) in theimaging device 1.

The voltage applier 130 a is connected to the auxiliary electrodes 103in the pixel cells 100 and 100 a through a wire 110. The capacitance 140is connected between the wire 110 and ground. In this embodiment, thecapacitance 140 is provided in correspondence to the pixel cell 100.However, the capacitance 140 is common to the pixel cells 100 and 100 a.

Similarly, the voltage applier 130 b is connected to the auxiliaryelectrodes 113 in the pixel cells 101 and 101 a through a wire 111. Thecapacitance 141 is connected between the wire 111 and ground. In thisembodiment, the capacitance 141 is provided in correspondence to thepixel cell 101. However, the capacitance 141 is common to the pixelcells 101 and 101 a.

In the structure described above, the voltage supply circuit 130 canapply individual voltages to the auxiliary electrodes 103 in the pixelcells 100 and 100 a and to the auxiliary electrodes 113 in the pixelcells 101 and 101 a.

In this embodiment, the voltage applier 130 a applies a voltage V1 tothe auxiliary electrode 103 through the wire 110, and the voltageapplier 130 b applies a voltage V2 to the auxiliary electrode 113through the wire 111. A voltage V3 is applied to the counter electrode105 from an counter voltage supply circuit (not illustrated). As anexample, the voltage V1 is higher than the voltage V2. The voltage V3 ishigher than the voltage V1. A voltage V4 at the pixel electrodes 102 and112 is lower than the voltage V2. In this case, the difference inpotential between the auxiliary electrode 103 and the counter electrode105 is lower than the difference in potential between the auxiliaryelectrode 113 and the counter electrode 105. As a result, in the pixelcells 100 and 100 a, positive holes generated in the vicinity of theauxiliary electrode 103 are more likely to flow into the pixel electrode102 than in the pixel cells 101 and 101 a. That is, the effectivesensitivity areas of the pixel cells 100 and 100 a become larger thanthe effective sensitivity areas of the pixel cells 101 and 101 a.Therefore, the sensitivities of the pixel cells 100 and 100 a can bemade higher than the sensitivities of the pixel cells 101 and 101 a.That is, it becomes possible to control the size of the effectivesensitivity area according to the applied voltage. In an application ofthis, the voltages V1 and V2 may be dynamically changed according to,for example, illuminance during photography.

In this embodiment, the capacitance 140 is provided for the wire 110 andthe capacitance 141 is provided for the wire 111. Thus, after thevoltage supply circuit 130 has output voltages, even if the output stateof the voltage supply circuit 130 is placed in a floating state, theoutput voltages are held in the capacitances 140 and 141. A switch maybe provided at an intermediate point of each of the wires 110 and 111 inthe vicinity of the output side of the voltage supply circuit 130. Afterthe voltage supply circuit 130 has output voltages, these switches maybe turned off. Even in this case, the output voltages are held in thecapacitances 140 and 141. That is, the capacitances 140 and 141 sampleand hold the voltages output from the voltage supply circuit 130. Thevoltage held in the capacitance 140 and the voltage held in thecapacitance 141 respectively continue to be applied to the auxiliaryelectrodes 103 and 113.

FIG. 4 schematically illustrates a relationship between sensitivityoutput and voltage applied to the auxiliary electrode. Sensitivityoutput is equivalent to the size of the effective sensitivity area ofthe pixel cell. When the voltage to be applied to the auxiliaryelectrode is changed, sensitivity output changes. If a detected chargeis a positive hole, when the voltage to be applied to the auxiliaryelectrode is increased, the sensitivity output of the pixel cell isincreased. If, for example, a relatively high voltage is applied to theauxiliary electrode 103, the sensitivity of the pixel cell 100 israised. By contrast, if, for example, a relatively low voltage isapplied to the auxiliary electrode 113, the sensitivity of the pixelcell 101 is lowered.

In this embodiment, the capacitances 140 and 141 are respectivelyconnected to the auxiliary electrodes 103 and 113. Therefore, even ifthe voltage to be applied to the auxiliary electrode is varied due todisturbance noise or the like, the potential of the auxiliary electrodeis less likely to vary. This makes it possible to perform imaging in astate in which sensitivity is more stable.

As described above, the imaging device 1 according to this embodimenthas the capacitances 140 and 141 that are provided in correspondence toat least two pixel cells 100 and 101 of a plurality of pixel cells, thecapacitance 140 corresponding to the pixel cell 100, the capacitance 141corresponding to the pixel cell 101. Each of the plurality of pixelcells has the pixel electrode 102 or pixel electrode 112, the auxiliaryelectrode 103 or 113, which is respectively insulated electrically fromthe pixel electrode 102 or 112 and is respectively disposed around thepixel electrode 102 or 112 in a plan view, the counter electrode 105,which faces the pixel electrode 102 or pixel electrode 112 and alsofaces the auxiliary electrode 103 or auxiliary electrode 113, and thephotoelectric conversion film 104 sandwiched between the counterelectrode 105 and the pixel electrode 102 or pixel electrode 112 andbetween the counter electrode 105 and the auxiliary electrode 103 or113, photoelectric conversion film 104 converting light into charges.The capacitances 140 and 141 are respectively connected to the auxiliaryelectrodes 103 and 113 in their respective pixel cells.

The capacitance 140 is connected to the auxiliary electrode 103 in thepixel cell 100, and the capacitance 141 is connected to the auxiliaryelectrode 113 in the pixel cell 101. When voltages are individuallyapplied to the capacitances 140 and 141 and are held in them, thesensitivities of the pixel cells 100 and 101 can be independentlyadjusted. The sensitivities of the pixel cells 100 and 101 can also bedynamically adjusted. Therefore, when, for example, the sensitivity of apixel cell having extremely high illuminance is dynamically suppressed,saturation of charges generated in the pixel cell can be suppressed, andthis enables wide dynamic range photography.

Since the voltage applied to the capacitance 140 is held in it and thevoltage applied to the capacitance 141 is held in it, it is possible tomaintain the sensitivity of the pixel cell 100 to which the capacitance140 is connected and the sensitivity of the pixel cell 101 to which thecapacitance 141 is connected. Thus, global shuttering, in whichexposures start at the same time, becomes possible in a state in whichthe pixel cells 100 and 101 have different sensitivities.

The imaging device 1 according to this embodiment also includes thepixel cells 100 and 100 a disposed in the first area and the pixel cells101 and 101 a disposed in the second area. The imaging device 1according to this embodiment also includes the capacitance 140 connectedin common to the auxiliary electrodes 103 in the pixel cells 100 and 100a and the capacitance 141 connected in common to the auxiliaryelectrodes 113 in the pixel cells 101 and 101 a.

As described above, since a capacitance common to a plurality of pixelcells in each of two areas in the imaging area is provided, sensitivitycan be individually adjusted for each of the two areas. In photographyin which different sensitivities are set for different columns, forexample, two images having different sensitivities, that is, an imagecorresponding to pixel cells in an even-numbered column and an imagecorresponding to pixel cells in an odd-numbered column, are obtained inone photography.

The imaging device 1 according to this embodiment further has thevoltage supply circuit 130 that applies a voltage to each capacitance.

Thus, since the imaging device 1 has the voltage supply circuit 130, aindividual voltage can be individually applied to each capacitancewithout having to externally provide a voltage supply circuit.

Second Embodiment

Next, an imaging device according to a second embodiment will bedescribed with reference to FIGS. 5A and 5B.

The imaging device 2 according to the second embodiment differs from theimaging device 1 in the first embodiment in that the imaging device 2has a switch 135 a that makes or breaks a connection between the voltagesupply circuit 131 and the auxiliary electrode 103 in the pixel cell 100and between the voltage supply circuit 131 and the auxiliary electrode103 in the pixel cell 100 a and also has a switch 135 b that makes orbreaks a connection between the voltage supply circuit 131 and theauxiliary electrode 113 in the pixel cell 101 and between a voltagesupply circuit 131 and the auxiliary electrode 113 in the pixel cell 101a. In other respects excluding the voltage supply circuit 131 andswitches 135 a and 135 b, the structure of the imaging device 2 is thesame as in the first embodiment. Therefore, the imaging device 2 will bedescribed below, mainly focusing on the operations of the voltage supplycircuit 131 and switches 135 a and 135 b.

FIG. 5A schematically illustrates electrical connections between thevoltage supply circuit 131 and the auxiliary electrode 103 in the pixelcell 100 and between the voltage supply circuit 131 and the auxiliaryelectrode 103 in the pixel cell 100 a and electrical connections betweenthe voltage supply circuit 131 and the auxiliary electrode 113 in thepixel cell 101 and between the voltage supply circuit 131 and theauxiliary electrode 113 in the pixel cell 101 a, in the imaging device 2according to the second embodiment.

The voltage supply circuit 131 has one voltage applier that generatespredetermined voltages. The voltage supply circuit 131 can applyvoltages to a plurality of pixel cells including the pixel cells 100 and100 a through the switch 135 a and can also apply voltages to aplurality of pixel cells including the pixel cells 101 and 101 a throughthe switch 135 b. Predetermined voltages applied to control the switches135 a and 135 b, predetermined voltages applied to the pixel cells 100and 100 a, and predetermined voltages applied to the pixel cells 101 and101 a are appropriately determined in response to, for example, commandsentered by the manipulator manipulating the imaging device 2 or commandsfrom the controller 202 (see FIG. 1) in the imaging device 2.

When, in this structure, the switches 135 a and 135 b are selectivelyturned on, a single voltage supply circuit 131 can be used to applyindividual voltages to the auxiliary electrodes 103 and 113. Although,in the first embodiment, the voltage supply circuit 130 has had twoindependent voltage appliers 130 a and 130 b, the voltage supply circuit131 in this embodiment has only one voltage supply circuit. According tothis embodiment, therefore, the number of voltage supply circuits can besubstantially reduced, so the imaging module including the imagingdevice 2 and the like can be made compact.

In this embodiment, the voltage supply circuit 131 applies the voltageV1 to the auxiliary electrode 103 through the wire 110 and also appliesthe voltage V2 to the auxiliary electrode 113 through the wire 111. Forexample, the voltage V1 is higher than the voltage V2. As a result, thesizes of the effective sensitivity areas of the pixel cells 100 and 100a become larger than the sizes of the effective sensitivity areas of thepixel cells 101 and 101 a. Accordingly, the sensitivities of the pixelcells 100 and 100 a can be made higher than the sensitivities of thepixel cells 101 and 101 a. That is, it becomes possible to control thesize of the effective sensitivity area according to the voltage to beapplied. In an application of this, the voltages V1 and V2 may bedynamically changed according to, for example, illuminance duringphotographing.

FIG. 5B is a timing diagram illustrating timing when the voltage supplycircuit 131 changes the voltages V1 and V2 in the imaging device 2 inthis embodiment. In FIG. 5B, “switch 135 a” indicates the state of theswitch 135 a, “switch 135 b” indicates the state of the switch 135 b, VOindicates a voltage output by the voltage supply circuit 131, V1indicates the voltage V1 to be applied to the auxiliary electrode 103,and V2 indicates the voltage V2 to be applied to the auxiliary electrode113.

As illustrated in the timing diagram in FIG. 5B, if, for example,illuminance is relatively high, when the voltage V1 is set to an MIDlevel, which is an intermediate level between a low level and a highlevel and the voltage V2 is set to the low level, it is possible tolower the sensitivity and thereby to suppress saturation in the pixelcell. If illuminance is low to the extent that saturation does not occurin the pixel, when the voltage V1 is set to the high level and voltageV2 is set to the intermediate MID level, the sensitivity of the pixelcell can be raised.

In this embodiment, since the size of the effective sensitive area ofthe pixel cell is controlled according to the illuminance, thesensitivity can be dynamically modulated. When individual sensitivitiesare optimized according to the photography scene, the dynamic range canbe expanded.

As described above, the imaging device 2 according to this embodimentfurther has the switches 135 a and 135 b, which are respectivelyprovided in correspondence to the capacitances 140 and 141. The voltagesupply circuit 131 individually applies a voltage to the capacitance 140through the switch 135 a and also individually applies a voltage to thecapacitance 141 through the switch 135 b.

Thus, voltages can be individually applied to the capacitances 140 and141 by a single voltage supply circuit 131, and this enables a voltagesupply circuit to be simplified.

Third Embodiment

Next, an imaging device according to a third embodiment will bedescribed with reference to FIGS. 6A and 6B.

The imaging device 3 according to the third embodiment differs from theimaging device 2 according to the second embodiment in that the imagingdevice 3 has scanning transistors 134 a to 134 d, each of which isdisposed in correspondence to one pixel cell, a row scanning circuit 160placed in the row direction, and a column scanning circuit 162 placed inthe columnar direction.

FIG. 6A schematically illustrates electrical connections among theauxiliary electrodes 103 and 113, voltage supply circuit 131, rowscanning circuit 160, and column scanning circuit 162 in the imagingdevice 3 according to the third embodiment.

The voltage supply circuit 131 generates predetermined voltages. Thevoltage supply circuit 131 can apply individual voltages to pixel cells150 a to 150 d through the transistors 134 a to 134 d and transistors136 a and 136 b. The transistors 134 a to 134 d are connected to the rowscanning circuit 160. The transistors 136 a and 136 b are connected tothe column scanning circuit 162. Voltages applied to control thetransistors 134 a to 134 d and transistors 136 a and 136 b andpredetermined voltages applied to the pixel cells 100, 100 a, 101, and101 a are appropriately determined in response to, for example, commandsentered by the manipulator manipulating the imaging device 3 or commandsfrom the controller 202 (see FIG. 1) in the imaging device 3.

In this embodiment, capacitances 140 a to 140 d are respectivelyprovided in correspondence to the pixel cells 150 a to 150 d.Specifically, the capacitance 140 a is connected between ground and apoint at which the output terminal (the drain terminal, for example) ofthe transistor 134 a and the auxiliary electrode 103 in the pixel cell150 a are connected. Similarly, each of the capacitances 140 b to 140 dis connected between ground and a point at which the output terminal ofthe relevant transistor 134 b, 134 c, or 134 d and the auxiliaryelectrode 103 or 113, whichever is appropriate, in the relevant pixelcell 150 b, 150 c, or 150 d.

FIG. 6B is a timing diagram illustrating timing when the voltage supplycircuit 131 changes voltage for each area in the imaging device 3according to the third embodiment. In this drawing, “verticalsynchronous signal” indicates a timing at which one frame starts,“horizontal synchronous signal” indicates a timing at which one linestarts, “scanning address (x, y)” indicates that a column to be selectedby the column scanning circuit 162 is the (x+1)th column and a row to beselected by the row scanning circuit 160 is the (y+1)th row, and V(x, y)indicates a voltage output from the voltage supply circuit 131 to thepixel cell positioned in the (x+1)th column and (y+1)th row. In theimaging device 3, pixel cells are placed in a matrix of (m+1) columnsand (n+1) rows; x is an integer that is at least 0 and at most m, and yis an integer that is at least 0 and at most n.

At a timing at which a vertical synchronous signal and a horizontalsynchronous signal are input, scanning address (0, 0) is selected by therow scanning circuit 160 and column scanning circuit 162 and the voltagesupply circuit 131 outputs voltage V(0, 0). Thus, the voltage V(0, 0) isapplied to the auxiliary electrode 103 in the area indicated by scanningaddress (0, 0) and to the capacitance 140 a. Since the voltage V(0, 0)is held in the capacitance 140 a, even if scanning address (0, 0) isdeselected, voltage V(0, 0) applied to the auxiliary electrode 103 andcapacitance 140 a is maintained.

The value of x in the scanning address is sequentially incremented.During one horizontal synchronous period, addresses in all columns areselected. The voltage supply circuit 131 outputs a voltage correspondingto each address.

At a timing at which a next horizontal synchronous signal is input, thevalue of the y address is incremented. Similarly, the value of x in thescanning address is sequentially incremented, starting from scanningaddress (0, 1). The voltage supply circuit 131 outputs a voltagecorresponding to each address.

In this embodiment, since the sizes of the effective sensitive areas ofa plurality of areas are controlled by a single voltage supply circuit131, the sensitivity can be dynamically modulated for each area. Whenthe sensitivities of individual areas are optimized according to thephotography scene, the dynamic range can be expanded.

As described above, in the imaging device 3 in this embodiment, thecapacitances 140 a to 140 d are respectively provided in correspondenceto a plurality of pixel cells 150 a to 150 d, which aretwo-dimensionally placed in the row direction and column direction. Theimaging device 3 further has the row scanning circuit 160 and columnscanning circuit 162. The row scanning circuit 160 drives thetransistors 134 a to 134 d and the transistors 136 a and 136 b on aper-row basis. The column scanning circuit 162 drives these transistorson a per-column basis.

Thus, voltages can be applied to the capacitances 140 a to 140 d, whichare respectively provided in correspondence to the pixel cells 150 a to150 d on a per-row or per-column basis. Therefore, application ofvoltages to all of the pixel cells 150 a to 150 d is completed at highspeed.

Fourth Embodiment

Next, an imaging device according to a fourth embodiment will bedescribed with reference to FIGS. 7A and 7B.

The imaging device 4 according to the fourth embodiment differs from theimaging device 3 according to the third embodiment in that a voltagesupply circuit 132 is connected to each signal line, which is providedfor one column, and that the imaging device 4 lacks a column scanningcircuit.

FIG. 7A schematically illustrates electrical connections among, in theimaging device 4 according to the fourth embodiment, the auxiliaryelectrodes 103 in the pixel cells 100 and 100 a, the auxiliaryelectrodes 113 in the pixel cells 101 and 101 a, the row scanningcircuit 160, and the voltage supply circuit 132 including the voltageappliers 132 a and 132 b, each of which is provided for one column.

The voltage supply circuit 132 has the voltage appliers 132 a and 132 b,each of which is provided for one column and independently generates apredetermined voltage. The voltage supply circuit 132 can applyindividual voltages to the pixel cells 150 a to 150 d through theirrespective transistors 134 a to 134 d. The transistors 134 a to 134 dare connected to the row scanning circuit 160 and the voltage applier132 a or 132 b, whichever is appropriate. Predetermined voltages appliedto control the transistors 134 a to 134 d, predetermined voltagesapplied to the pixel cells 100 and 100 a, predetermined voltages appliedto 101 and 101 a are appropriately determined in response to, forexample, commands entered by the manipulator manipulating the imagingdevice 4 or commands from the controller 202 (see FIG. 1) in the imagingdevice 4.

FIG. 7B is a timing diagram illustrating timing when the voltage supplycircuit changes voltage for each area in the imaging device 4 accordingto the fourth embodiment. Items in this drawing are substantially thesame as in FIG. 6B referenced in the third embodiment, except that, inthis embodiment, “scanning address (x, y)” in the third embodiment isreplaced with “scanning address (y). Vfz(x, y) indicates a voltageoutput from the voltage supply circuit 132 to the pixel cell positionedin the (x+1)th column and (y+1)th row in a z frame period. In theimaging device 4, pixel cells are placed in a matrix of (m+1) columnsand (n+1) rows; x is an integer that is at least 0 and at most m, and yis an integer that is at least 0 and at most n.

In this embodiment, the active matrix method is used to apply voltagesindividually to the auxiliary electrodes 103 and 113 in all of the pixelcells 150 a to 150 d and to the capacitances 140 a to 140 d.Specifically, scanning address (0) is first selected by the row scanningcircuit 160 at a timing at which a vertical synchronous signal and ahorizontal synchronous signal are input, after which the voltage supplycircuit 132 outputs voltages Vf0(0, 0) to Vf0(m, 0) corresponding to therelevant column addresses. Thus, voltages Vf0(0, 0) to Vf0(m, 0) areapplied to scanning address (0), that is, the auxiliary electrodes 103and 113 in the area in the first row, and to the capacitances 140 a and140 b. Since voltages Vf0(0, 0) to Vf0(m, 0) are held in thecapacitances 140 a and 140 b even if scanning address (0) is deselected,voltages Vf0(0, 0) to Vf0(m, 0) are maintained.

At a timing at which a next horizontal synchronous signal is input, thevalue of the y address is incremented. The voltage supply circuit 132outputs a voltage corresponding to each column address. Thus, voltagesVf0(0, 1) to Vf0(m, 1) are applied to scanning address (1), that is, theauxiliary electrodes 103 and 113 in the pixel cells in the second row,and to the capacitances 140 c and 140 d. Since voltages Vf0(0, 1) toVf0(m, 1) are held in the capacitances 140 c and 140 d even if scanningaddress (1) is deselected, voltages Vf0(0, 1) to Vf0(m, 1) aremaintained. For all subsequent scanning addresses (y), voltages Vf0 areapplied to the auxiliary electrodes 103 and 113 and the capacitances 140c and 140 d in a similar manner and are held in the capacitances 140 cand 140 d. During one frame period, application of voltages to all pixelcells is completed in this way. This application of voltages to allpixels in one frame period is repeated for each frame.

In this embodiment, the voltage supply circuit 132 having the voltageappliers 132 a and 132 b, each of which is provided for one column, isused to control the size of the effective sensitivity area of each of aplurality of areas. Thus, it is possible to dynamically modulatesensitivity for each area at high speed. When the sensitivities ofindividual areas are optimized according to the photography scene, thedynamic range can be expanded.

As described above, in the imaging device 4 in this embodiment, thepixel cells 150 a to 150 d are two-dimensionally placed in the rowdirection and column direction. The voltage supply circuit 132 has thevoltage appliers 132 a and 132 b, each of which is provided for onecolumn. The voltage applier 132 a applies a voltage to the capacitances140 a and 140 c in the pixel cells 150 a and 150 c placed in therelevant column. Similarly, the voltage applier 132 b applies a voltageto the capacitances 140 b and 140 d in the pixel cells 150 b and 150 dplaced in the relevant column. The row scanning circuit 160 drives thetransistors 134 a to 134 d, which are provided in correspondence to thepixel cells 150 a to 150 d, on a per-row basis.

Thus, individual voltages can be applied to the capacitances 140 a to140 d, which are respectively provided in correspondence to the pixelcells 150 a to 150 d, in the active matrix method. Therefore,application of voltages to all of the pixel cells 150 a to 150 d iscompleted at high speed and with various sensitivity settings.

Fifth Embodiment

Next, an image module according to a fifth embodiment will be describedwith reference to FIG. 8.

FIG. 8 is a schematic block diagram illustrating the structure of theimaging module 5 according to the fifth embodiment. The imaging module 5has an optical system 220 including a lens and a diaphragm, an imagingdevice 221, a camera signal processor 222, and a system controller 223.These constituent elements are typically mounted on a printed circuitboard. The imaging module 5 is, for example, a digital still camera, amedical camera, a monitoring camera, a vehicle-mounted camera, a digitalsingle-lens reflex camera, or a digital mirror-less single-lens camera.

As the imaging device 221, any one of the imaging device 1 in the firstembodiment to the imaging device 4 in the fourth embodiment can be used.

The camera signal processor 222 is formed from a semiconductor elementor the like. The camera signal processor 222 can be implemented by, forexample, an image signal processor (ISP). The camera signal processor222 processes an image signal output from the imaging device 221, andoutputs the resulting image data.

The system controller 223 is implemented by, for example, a centralprocessing unit (CPU) specific to a module. The system controller 223controls the whole of the imaging module 5.

In this embodiment, an imaging module can be provided that suppressessaturation in low-sensitivity pixels and thereby enables wide dynamicrange photography.

As described above, the imaging module 5 according to this embodimenthas the imaging device 221 equivalent to the imaging device in any oneof the above embodiments and also has the camera signal processor 222that processes an image signal output from the imaging device 221 andcreates image data.

Accordingly, an imaging module having the imaging device 221 thatenables wide dynamic range photography is implemented.

So far, the imaging device and imaging module in the present disclosurehas been described according to the first to fifth embodiments. However,the present disclosure is not limited to these first to fifthembodiments. The range of one or a plurality of aspects may includeembodiments in which various variations that a person having ordinaryskill in the art thinks of are applied to the embodiments describedabove and may also include other embodiments in which part of theconstituent elements in the embodiments described above are combined,without departing from the intended scope of the present disclosure.

In the first and second embodiments, for example, the first area andsecond area, in each of which a capacitance is shared, have respectivelycorresponded to pixel cells in an even-numbered column and anodd-numbered column in the imaging area. However, this is not alimitation on the segmentation of the first area and second area. Thefirst area and second area may correspond to pixel cells in both aneven-numbered row and an odd-numbered row. Alternatively, one of twopixel cell groups placed in a checkered pattern may correspond to thefirst area, and the other may correspond to the second area.

The imaging device and imaging module in the present disclosure can beapplied to, for example, sensor systems and various camera systemsincluding a digital still camera, a medical camera, a monitoring camera,a vehicle-mounted camera, a digital single-lens reflex camera, and adigital mirror-less single-lens camera.

What is claimed is:
 1. An imaging device comprising: at least one pixelcell that includes a first pixel cell, each of the at least one pixelcell including a photoelectric conversion layer having a first surfaceand a second surface opposite to the first surface, a pixel electrode onthe first surface, an auxiliary electrode on the first surface, theauxiliary electrode surrounding the pixel electrode and beingelectrically insulated from the pixel electrode, a counter electrode onthe second surface, the counter electrode facing both of the pixelelectrode and the auxiliary electrode, and a charge detection circuitconnected to the pixel electrode; a voltage supply circuit that suppliesa voltage; a first switch that switches between electrical connectionand electrical disconnection; a first capacitor that has one endconnected to the auxiliary electrode of the first pixel cell and theother end held to a predetermined voltage; and a first control circuitconnected to the first switch, the first control circuit causing thefirst switch to switch between electrical connection and electricaldisconnection, wherein the voltage supply circuit is connected, throughthe first switch, to the auxiliary electrode of the first pixel cell andto the one end of the first capacitor.
 2. The imaging device accordingto claim 1, wherein the at least one pixel cell includes a second pixelcell, and the auxiliary electrode of the second pixel cell is connectedto the auxiliary electrode of the first pixel cell and to the one end ofthe first capacitor, and the voltage supply circuit is connected,through the first switch, to the auxiliary electrode of the second pixelcell.
 3. The imaging device according to claim 1, further comprising: asecond capacitor; a second switch that switches between electricalconnection and electrical disconnection; and a second control circuitconnected to the second switch, the second control circuit causing thesecond switch to switch between electrical connection and electricaldisconnection, wherein the at least one pixel cell includes a secondpixel cell, the second capacitor has one end connected to the auxiliaryelectrode of the second pixel cell and the other end held to apredetermined voltage, the voltage supply circuit applies a firstvoltage to the auxiliary electrode of the first pixel cell through thefirst switch, and the voltage supply circuit applies a second voltagedifferent from the first voltage, to the auxiliary electrode of thesecond pixel cell through the second switch.
 4. The imaging deviceaccording to claim 1, wherein the voltage supply circuit includes thefirst switch.
 5. The imaging device according to claim 3, wherein thevoltage supply circuit includes the first switch and the second switch.6. The imaging device according to claim 1, wherein the first controlcircuit includes a first scanning circuit and a second scanning circuit,the first scanning circuit and the second scanning circuit beingconnected to the first switch, and the first switch switches betweenelectrical connection and electrical disconnection based on both of asignal from the first scanning circuit and a signal from the secondscanning circuit.
 7. The imaging device according to claim 1, whereinthe first control circuit includes a first scanning circuit connected tothe first switch, and the first switch switches between electricalconnection and electrical disconnection based on a signal from the firstscanning circuit.
 8. An imaging module comprising the imaging deviceaccording to claim 1, and a camera signal processor that generates imagedata by processing an image signal output from the imaging device.